The present disclosure relates to gas turbine engines, and more particularly to an exhaust duct therefor.
Gas turbine engines, such as those which power modern military and commercial aircraft, include a compressor section to pressurize a supply of air, a combustor section to burn a hydrocarbon fuel in the presence of the pressurized air, and a turbine section to extract energy from the resultant combustion gases and generate thrust. Downstream of the turbine section, military aircraft engines often include an augmentor section, or “afterburner”, operable to selectively increase thrust. The increase in thrust is produced when fuel is injected into the core exhaust gases downstream of the turbine section and burned with the oxygen contained therein to generate a second combustion.
The augmentor section and downstream exhaust duct and nozzle sections may be exposed to high temperature exhaust gases such that a liner assembly is disposed between the exhaust gas and the exhaust duct to provide thermal protection and/or acoustic damping. These may be of single or double walled construction, with a hot sheet and a cold sheet. The hot sheet may have a thermal barrier or radar signature reduction coating. The exhaust gas temperatures may in some instances exceed the metallic alloy capabilities in these sections such that film cooling is provided therefor. The cooling air is provided though numerous cooling holes to sheath the hardware from the exhaust gases. The cooling holes are typically produced via a laser drill through the coated substrate.